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Question
Draw a graph from the following data. Draw tangents at x = 2, 4, 6 and 8. Find the slopes of these tangents. Verify that the curve draw is y = 2x2 and the slope of tangent is \[\tan \theta = \frac{dy}{dx} = 4x\]
\[\begin{array}x & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 & 10 \\ y & 2 & 8 & 18 & 32 & 50 & 72 & 98 & 128 & 162 & 200\end{array}\]
Solution
Note: Students should draw the graph y = 2x2 on a graph paper for results.
To find a slope at any point, draw a tangent at the point and extend the line to meet the x-axis. Then find tan θ as shown in the figure.
The above can be checked as follows:
\[Slope = \tan \theta = \frac{dy}{dx}\]
\[ = \frac{d}{dx}\left( 2 x^2 \right) = 4x\]
Here, x = x-coordinate of the point where the slope is to be measured.
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